Mauer left the Twins game against the Orioles in the eighth inning on Saturday night with what was diagnosed to be left hamstring tightness.
The catcher suffered the injury when he rounded second base going from first to third on a Torii Hunter double. Mauer was running fine from first to second, but after stepping on the bag with his right foot, he felt his left hamstring grab. From that point, Mauer had trouble making it to third. He limped for the final 45 feet or so of his run.
Mauer said he did not feel anything in the leg until that point in the game, and afterward he was clearly frustrated.
"It's real sore right now," Mauer said after the game. "I guess we'll just have to wait to find out what it is. Hopefully, it doesn't take too long."
Twins manager Ron Gardenhire said the team will view Mauer's status as day-to-day for now and see how the catcher feels on Sunday morning. With only one healthy catcher in Mike Redmond, the club will call up Chris Heintz from Triple-A Rochester and have him arrive in time for Sunday's finale against the Orioles. The corresponding roster move will not be announced until Sunday.
This is the second injury that Mauer has suffered in the past week. Mauer injured his left ankle in Tuesday's game vs. the Mariners during a fifth-inning play at home plate in which he tagged out Jose Guillen. Mauer taped up the ankle and finished that game, but he was given the day off on Wednesday.
Mauer also missed 29 games earlier this season after he strained his left quadriceps muscle. The Twins were forced to play nearly all of May and part of early June without their starting catcher. But this injury comes at an even more inopportune time as the club tries to work its way back into the division hunt.
"We missed him once already, and we can't try to miss him twice," Hunter said. "But the most important thing now is he gets healthy. Hopefully, it's not that bad."
Kelly Thesier is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.